The attack on a newspaper office in Paris shows us that the war with Islamist terrorism is not just something going on in Syria. As President Obama said, “these kinds of attacks can happen anywhere in the world.”

In Paris on Wednesday attackers armed with automatic weapons hit the offices of the satirical French newspaper Charlie Hebdo, killing 12 including the editorial director. The magazine was firebombed in 2011 for running depictions of Mohammed, and the attackers today reportedly said afterwards “We have avenged the prophet.” Charlie Hebdo had also sent out an anti-Islamic State tweet shortly before the attack, which could have been a trigger, though one eyewitness said the group claimed to be tied to al Qaeda in Yemen.

President Obama strongly condemned the shooting and said that the United States would “provide any assistance needed to help bring these terrorists to justice.” Immediately recognizing that this domestic incident as an act of terrorism was a turnaround for the White House. The administration initially hesitated to use that label after the 2009 Ft. Hood massacre and the 2013 Boston Marathon, waiting until an international connection could be proved.

However, incidents like these are terrorist acts on their face, whether or not the attackers are formally connected to the Islamic State, al Qaeda or any other such group. For several years al Qaeda has promoted small-scale, fast attacks in western cities — so-called jihad-in-place — through its English-language publication Inspire. This is the magazine that ran an article on how to build the type of pressure cooker bomb that Dzhokhar and Tamerlan Tsarnaev allegedly used in Boston. We saw the same dynamic at work in the October 2014 attack in Ottawa, Canada by homegrown radical Michael Zehaf-Bibeau. Jihad-in-place is safer for terrorists, since they risk capture traveling to and from hotspots like Syria and Afghanistan. It is harder for security forces to detect and prevent. And it can be very effective.

Jihad-in-place works best when there are pre-existing radical networks inside a target country. France has more than its share of homegrown extremists, and there is no question about the motive for the Charlie Hebdo attack. The terrorists were captured on video shouting the Islamist battle cry “Allahu Akbar.” Ft. Hood shooter Nidal Hasan said the same thing when he opened fire, though this was later downplayed in an attempt to strip away the inspiration for his act of “workplace violence.“ But as the number of such attacks increases, it becomes less credible to write them off as isolated incidents. They occur in different locations, but they are linked by a common ideology, and a common enemy, western civilization. This radical extremist outlook is the collective root cause of Islamist terrorism. The fact that the Paris jihadists targeted a magazine shows that they believe in the war of ideas literally.

The Charlie Hebdo attack shows once again that the terrorists will not limit their struggle to active war zones like Syria and Iraq. It also demonstrates the interconnectedness of violent radical groups motivated by the same ideals and pursuing the same goals, whether or not they are technically members of the same organization. And it tells us that the war on terrorism cannot simply be won by sending fleets of drones to Yemen or dropping remotely guided munitions in Syria. Unless we address the ideological root causes of Islamist extremism, the terrorists will keep seeking ways to bring the war home to us.

James S. Robbins, author of The Real Custer: From Boy General to Tragic Hero, is a member of USA TODAY’s Board of Contributors.